Relationships between the lean content of joints and overall lean content in steer carcasses of different breeds and crosses

Abstract

SUMMARY Dissection data for 753 steer carcasses from 17 breed-type x feeding system groups were used to examine the prediction of lean content in the side (half carcass) from the lean content of standardized wholesale joints. Different prediction equations were examined and the joints compared both in terms of predictive precision and the stability of their prediction equations between groups. The relative precision of the joints for predicting weight of lean in the side depended on whether or not the prediction equation included joint weight. With side weight and weight of lean in joint as independent variates, there was little difference between most joints in precision, and the smaller joints, shin and leg (hind shin) appeared to be best because they are convenient and easy to dissect. The addition of joint weight to the equation improved considerably the precision of all the joints except the shin and leg. The coast and top piece gave the most precise predictions with the trivariate equation (residual standard deviations about the common regression line computed ignoring groups, RSD overall, were 1·44 and 1·48 kg respectively) and the fore rib probably offered the best compromise between cost and precision (RSD overall = 1·82 kg). The stability of prediction equations between groups was influenced in a similar way by the inclusion of joint weight as an independent variate. The joints which gave the most precise predictions tended to have the most stable equations. The average biases between the actual group means and the means predicted using the trivariate equation computed ignoring groups were ± 0·46, ± 0·49 and ± 0·76 kg for the top piece, coast and fore rib respectively.